This paper presents a bidirectional non-isolated dc-dc converter based on three-level flying-capacitor converters intended to be applied to electric railway systems. It consists of several main converters with four power devices per converter, multiple auxiliary converters each of which is formed by cascaded chopper cells, and inductors for current control. The dc-dc converter can achieve zero-current switching (ZCS) for all the power devices in the main converters, not only under steady-state conditions but also under transient-state conditions including sudden changes in the supply voltage. This paper presents a current control method based on dq0 transformation and a voltage control method for the floating dc capacitors used in the auxiliary converters. The validity of the control methods proposed in this paper is verified through experiments using a 200-V, 2-kW downscaled model.